U.S. patent application entitled "Process for making metal-matrix composites reinforced by ultrafine reinforcing materials" of U.S. Ser. No. 08/103,049 filed on Jul. 28, 1993, now U.S. Pat. No. 5,401,338 which is also invented by the same inventor of this application, disclosed a process for making metal-matrix composites by spraying or atomizing a suspension liquid containing the ultrafine reinforcing material into the molten metal matrix by using an inert gas of nitrogen.
The nitrogen inert gas is greatly consumed in such a conventional process under the circumstances as follows:
1. The nitrogen gas is used to help agitate the suspension liquid containing the reinforcing material before being charged to the molten metal.
2. The nitrogen should be continuously applied into the nozzle for spraying or atomizing the suspension liquid onto the molten metal solution.
3. The process is continuously blanketed with nitrogen.
Therefore, the great consumption of nitrogen in such a conventional process will increase a production cost of the composite products and will thus decrease its commercial value.